1. Field of the Invention
The present invention relates to a method for controlling a semiconductor manufacturing apparatus for processing wafers, and a control system of the semiconductor manufacturing apparatus.
2. Background Art
Conventionally, various monitoring methods are applied in the semiconductor manufacturing process. Among the methods, there is a method for monitoring a so-called QC (Quality Control) value, in which method physical quantities in the course of manufacturing process are measured.
For example, a resist value and a finished dimension value are measured in a lithography process. The measurement of QC value data takes much time, and hence, when the measurement is performed to all wafers, the productivity is lowered. Therefore, for example, there is a case where QC value data of one wafer in a lot are measured as a sample, so as to be used as representative values of the lot.
Here, the QC value data in the lithography process is used, for example, for determination of whether or not the lithography process is performed again (reworked). That is, when the measured resist dimension value as the QC value data is outside a prescribed value, the pattern exposure of the lot is judged to be unsuccessful, and the lithography process is performed again.
Even in this case, however, when the dimensional abnormality occurs in a wafer whose QC value data are not measured, the abnormality of the wafer may be overlooked.
On the contrary, even when the dimensional abnormality occurs in a wafer whose QC value data are measured, the dimension of wafers whose QC value data are not measured may be normal. In this case, unnecessary rework is performed.
Therefore, there is a risk that the cost of manufacturing process is increased, or that an abnormality is caused by the unnecessary rework even in an originally normal wafer.
On the other hand, the quality of a wafer processed by the semiconductor device manufacturing apparatus is affected by various internal states of the apparatus. For example, in the lithography process, various internal states of the apparatus, such as the states of focus control and exposure light quantity in the exposure device, or the resist coating temperature, affect the final resist dimension value.
Further, the relationship between these internal states of the apparatus and the dimension is not clarified, and a variation in the internal states may appear as an unexpected variation in the dimension. However, it has been difficult to specify in which part of the apparatus a factor affecting the dimension is located.
Here, among the conventional control systems of the semiconductor manufacturing apparatus, there is a system in which process state information, as information related to states of a process, acquired in time series during a period when each process step constituting the process is performed, and inspection result information regarding an object processed in the process are inputted, and in which a process-quality model representing a relationship between the process feature quantity extracted from the process state information and the inspection result information is created (for example, see Japanese Patent Laid-Open No. 2005-197323).
The above described control system of the semiconductor manufacturing apparatus predicts the quality of an object to be processed on the basis of the created process-quality model.
However, in some control systems of the semiconductor manufacturing apparatus, for example, there is a problem that when the process feature quantity used as the base of the process-quality model is changed with the lapse of time, deviation occurs between the quality predicted by the created process-quality model and the actually measured quality.